Sheet metal body stampings for automobile bodies are becoming larger, encompassing more and different areas of the vehicle body into a unitary panel. This reduces part count and increases quality and assembly productivity, but often requires that the blank to be stamped into the large body panel be comprised of two or more smaller subblanks of differing thicknesses. Greater thicknesses may be needed only in certain areas, and to make the entire panel that thick would represent a great cost and weight penalty. Typically, such a compound blank uses two sheet metal blanks laser welded together at abutted straight edges. The welding operation requires that the blanks be solidly fixtured and held together at the abutted edges.
FIG. 1 shows a typical apparatus used today to weld compound blanks. The fixturing and welding operations are combined in the same apparatus, which, while it sounds efficient, is actually not as efficient as it should be. The two blanks have to be pushed toward one another, into the apparatus, in order to bring the straight edges into abutment, between upper and lower edge clamps. The weld beam then runs along the abutted edge interface, assuming that the interface has been properly located. Proper blank and edge location is heavily dependent upon the blanks having been cut or sheared very close to their nominal size initially. Those skilled in the art will recognize that there is an inevitable variation in blank size, and in the angle subtended by the corners thereof, because of normal manufacturing tolerances. Moreover, the various positioning operations, manual or otherwise, that must be applied to the blanks to properly locate them, with the known apparatus, must be applied remote from the abutted edge interface, and that interface is not easily visible. All the positioning and clamping must be completed before the welding can be accomplished, which represents a process bottleneck that limits how quickly a complete cycle can be located.